340 1.4 rough ans slow idling

[Two340'sman]

Well, I'm back from my trip. The car started easily, and once warm tickover was a steady approx 900 RPM. Stop-start driving for 5 miles, car behaved perfectly, no stalling.

Did my work, cutting grass and hedge, started car again easily and once warm tickover good again, around 900 RPM. Got about half way back, and car stalled, restarted and tickover rough and about 400 RPM, after a few seconds all was back to normal, 900 RPM smooth tickover.

Drove the last 2.5 Miles, no problem. Parked car, and tickover dropped to about 500 RPM, revved engine a little and tickover good again, smooth 900 RPM.

Opened bonnet with engine running and pulled off the wire to the idle valve, engine immediately stalled. Replaced wire, started engine and good tickover again.

[Joe Harding]

Originally Posted by Two340'sman

Well, I'm back from my trip. The car started easily, and once warm tickover was a steady approx 900 RPM. Stop-start driving for 5 miles, car behaved perfectly, no stalling.

Did my work, cutting grass and hedge, started car again easily and once warm tickover good again, around 900 RPM. Got about half way back, and car stalled, restarted and tickover rough and about 400 RPM, after a few seconds all was back to normal, 900 RPM smooth tickover.

Drove the last 2.5 Miles, no problem. Parked car, and tickover dropped to about 500 RPM, revved engine a little and tickover good again, smooth 900 RPM.

Opened bonnet with engine running and pulled of the wire to the idle valve, engine immediately stalled. Replaced wire, started engine and good tickover again.

Well it will. The valve shuts off the idle flow. Try choking off the brake servo hose

[Two340'sman]

Originally Posted by Joe Harding

Well it will. The valve shuts off the idle flow. Try choking off the brake servo hose

Can do, what is the effect of this please?

[Joe Harding]

As posted earlier. Any air leak at idle will dilute the mix and cause rough idling. If your brake servo vacuum assist is bleeding air into the carburettor you will have such a leak.

[Laird Scooby]

Originally Posted by Two340'sman

Can do, what is the effect of this please?

Eliminates the possibility the brake servo is leaking which can cause similar symptoms. Usually they give trouble over a period of time though whereas your problem seems to have appeared suddenly.

[Two340'sman]

Originally Posted by Joe Harding

As posted earlier. Any air leak at idle will dilute the mix and cause rough idling. If your brake servo vacuum assist is bleeding air into the carburettor you will have such a leak.

Thanks, my problem seems to be intermittent, I cant really dive with the vacuum pipe blocked off as I wont have any brakes, or nearly none!

[Two340'sman]

Originally Posted by Laird Scooby

Eliminates the possibility the brake servo is leaking which can cause similar symptoms. Usually they give trouble over a period of time though whereas your problem seems to have appeared suddenly.

Thanks, my problem seems to be intermittent, I cant really dive with the vacuum pipe blocked off as I wont have any brakes, or nearly none!

[Laird Scooby]

Originally Posted by Two340'sman

Thanks, my problem seems to be intermittent, I cant really dive with the vacuum pipe blocked off as I wont have any brakes, or nearly none!

Something that does sometimes give trouble ins the NRV aka Non-Return Valve aka check-valve in the servo or in the hose that feeds it.

These are only a few quid to buy, the arrow should point to the engine /inlet manifold and you just need to know the right size for the hose bore. Also check the ends of the hose for fraying/splitting/perishing but it might be worth simply renewing the NRV as a precaution and see if your fault disappears :

https://www.ebay.co.uk/sch/i.html?_f...c&LH_PrefLoc=1

That should take you to a list on ebay of all the UK items, ascending in price. Find the bore of your hose and a matching valve and give it a go. Looking back over your pics, your NRV is in the hose between the servo and manifold more or less level with the back of the expansion tank. I can see some markings on the hose near the servo which might give a clue to the size too.

PS - as an aside when we digressed into electric conversions and i mentioned the NSU Ro80 and the original type of engine i referred to it by the inventors name which begins with a "W" and ends with a mis-spelling of "ankle" - i see the "profanity software" has edited the name of the inventor!

[Two340'sman]

Originally Posted by Laird Scooby

Something that does sometimes give trouble ins the NRV aka Non-Return Valve aka check-valve in the servo or in the hose that feeds it.

These are only a few quid to buy, the arrow should point to the engine /inlet manifold and you just need to know the right size for the hose bore. Also check the ends of the hose for fraying/splitting/perishing but it might be worth simply renewing the NRV as a precaution and see if your fault disappears :

https://www.ebay.co.uk/sch/i.html?_f...c&LH_PrefLoc=1

That should take you to a list on ebay of all the UK items, ascending in price. Find the bore of your hose and a matching valve and give it a go. Looking back over your pics, your NRV is in the hose between the servo and manifold more or less level with the back of the expansion tank. I can see some markings on the hose near the servo which might give a clue to the size too.

PS - as an aside when we digressed into electric conversions and i mentioned the NSU Ro80 and the original type of engine i referred to it by the inventors name which begins with a "W" and ends with a mis-spelling of "ankle" - i see the "profanity software" has edited the name of the inventor!

Thanks again, good idea the non return valve. Will look at that tomorrow. I do have my late Dad's Metro Vanden Plas here, that I know has a non return valve on the servo. I could nick that.

I knew exactly what rotary engine you were talking about.

This is a great forum, and thanks to everyone for their helpful suggestions.

[Laird Scooby]

Originally Posted by Two340'sman

Thanks again, good idea the non return valve. Will look at that tomorrow. I do have my late Dad's Metro Vanden Plas here, that I know has a non return valve on the servo. I could nick that.

I knew exactly what rotary engine you were talking about.

This is a great forum, and thanks to everyone for their helpful suggestions.

If memory serves, the NRV is integral with the servo banjo plug connector on Metros, you could probably find a universal one in Hellfrauds tomorrow and know that being new, it should work properly.

I thought you'd know about the rotary engine, i was just adding that bit for clarity and also to point out to the mods that i wasn't actually swearing!

Would i be right in guessing you're restoring/keeping in good condition your late dads VDP Metro?